The quality of life of a population is an important concern in clinical and health psychology. There are many components to well-being. A large part is standard of living, the amount of money and access to goods and services that a person has; these numbers are fairly easily measured. Others like freedom, happiness, art, environmental health, and innovation are far harder to measure. This has created an inevitable imbalance as programs and policies are created to fit the easily available economic numbers while ignoring the other measures, that are very difficult to plan for or assess.

Debate on quality of life is millennia-old, with Aristotle giving it much thought in his Nicomachean Ethics and eventually settling on the notion of eudaimonia, a Greek term often translated]] as [[happiness, as central. The neologism liveability (commonly but less correctly livability), from the adjective liveable, is an abstract noun now often applied to the built environment or a town or city, meaning its overall contribution to the quality of life of inhabitants.

Understanding quality of life is today particularly important in health care, where monetary measures do not readily apply. Decisions on what research or treatments to invest the most in are closely related to their effect of a patient's quality of life.

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The measures often used in the study of health care are 'quality-adjusted life years' (QALYs) and the related 'disability-adjusted life years' (DALYs); both equal 1 for each year of full-health life, and less than 1 for various degrees of illness or disability. Thus the cost-effectiveness of a treatment can be assessed by the cost per QALY or DALY it produces; for example, a cancer treatment which costs $10,000 and on average gives the patient 2 extra years of full health costs $5000 per QALY. Assessing treatments in this way avoids the much greater problems associated with putting a monetary value on life, as required in other areas of economics; saying that a treatment costs $5000 per QALY (i.e. per year of life) does not say or assume anything about the monetary value of a year of life.

Another method of measuring quality of life is by subtracting the "standard of living", according to the technical definition of the term. For example, people in rural areas and small towns are generally reluctant to move to cities, even if it would mean a substantial increase in their standard of living. One can thus see that the quality of life of living in a rural area is of enough value to offset a higher standard of living. Similarly people must be paid more to accept jobs that will lower their quality of life, night jobs, ones with extensive travel all pay more and the difference in salaries can also give a measure of the value of quality of life.

There is a growing field of research concerned with developing, evaluating and applying quality of life measures within health related research (eg within randomised controlled trials). Many of these focus on the measurement of health related quality of life (HRQoL), rather than a more global conceptualisation of quality of life. They also focus on measuring HRQoL from the perspective of the patient and thus take the form of self completed questionnaires. The International Society for Quality of Life was founded in response to this research and is a useful source of information on this topic.

A number of groups and agencies around the world have tried to develop ways of assessing quality of life: